The present invention is concerned with detecting the movement of a piston head and piston rod in a piston and cylinder device.
There are many circumstances in which piston and cylinder devices, which may be pneumatically or hydraulically operated, are utilized to move parts in machines and in which it is desired to know the precise position of the piston head and piston rod in the cylinder. Various types of transducer have been proposed for monitoring such position, but frequently suffer from disadvantages, for example bulk, fragility or undue sensitivity to hostile environments.
Glassware forming machines are particularly good examples of machines in which a hostile environment may affect transducers which are used to monitor the movement of parts.
It is one of the objects of the present invention to provide an improved piston and cylinder device having means for monitoring the position of the piston and piston rod.